The support of sending faxes over voice over IP (VoIP) is limited. Conventional voice codecs are not designed for facsimile (FAX) transmission. One solution to overcome the drawback is to treat the fax system as a message switching system which does not need real time data transmission. In such a system, a FAX is sent as an email attachment or remote printout using Internet Printing Protocol. The receiving device can buffer the incoming FAX data before displaying or printing the FAX image.
Another solution to transmitting FAX over VoIP is addressed in ITU-T Recommendation T.38. T.38 describes technical features for transferring facsimile documents in real-time between two standard Group 3 FAX terminals over the Internet or other networks using Internet Protocol (IP). The Recommendation allows the use of either Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) depending on the service environment. T.38 enabled devices enable use of ordinary FAX machines on modern networks, permitting Analog Telephone Adapters (ATAs) or other FAX over IP (FoIP) products to handle FAX calls through a VoIP service.
Unfortunately, T.38 usage and capability varies greatly between VoIP service providers. Some VoIP service providers do not support T.38 at all while other VoIP service providers support T.38 only partially. Despite a decline in conventional FAX due to Internet and e-mail FAX, the industry trend is to transparently support FAX using T.38.
Accordingly, there is a need to determine traffic routes within a communication network for providing a high quality of service (QoS) for certain traffic types.